Electrolytic cell

ABSTRACT

AN ELECTROLYTIC CELL HAS A REMOVABLE CONDUCTIVE WALL CARRYING SPACED PARALLED PLATE ELECTRODES. THE WALL IS COMPOSED OF A SERIES OF ELONGATED VERTICAL ELEMENTS WHICH ARE INDIVIDUALLY SECURED TO ADJACENT ELEMENTS BY MALE-FEMALE THREADED MEMBERS WHICH SCREW INTO ONE ANOTHER. THE BORDERS OF THE ELECTRODE PLATES ARE CLAMPED BETWEEN SUC-   CESSIVE WALL ELEMENTS WITH SELECTED PRESSURE BY INDIVIDUALLY TIGHTENING THE THREADED MEMBERS.

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3,700,582 ELECTROLYTIC CELL Umberto Giacopelli, Via Piave, Rosignano Solvay, Italy Filed Sept. 16, 1970, Ser. No. 72,566 Claims priority, application Germany, Sept. 18, 1969, P 19 47 157.9 Int. Cl. B01k 3/00 US. Cl. 204-275 12 Claims ABSTRACT OF THE DISCLOSURE An electrolytic cell has a removable conductive wall carrying spaced parallel plate electrodes. The wall is composed of a series of elongated vertical elements which are individually secured to adjacent elements by male-female threaded members which screw into one another. The borders of the electrode plates are clamped between successive wall elements with selected pressure by individually tightening the threaded members.

The present invention relates to improvements in the construction of electrolytic cells having vertical unipolar metal electrodes with the cathodic elements alternating with anodic elements.

More particularly, the invention resides in the concept of an exterior side wall conductively and removably supporting electrodes of the same polarity.

This wall is advantageously utilized to support the anodes in a cell for the electrolytic preparation of chlorine, hypochlorites or chlorates.

There has already been proposed in US. Patent 3,055,- 821 an electrolytic cell for the preparation of chlorates in which an exterior lateral wall carries a removable metallic plate which supports titanium anodes. The anodic assem'bly must necessarily be withdrawn laterally from the cell like a drawer and this requires considerable lateral space at the side of the removable wall and consequently prevents the side-by-side disposition of cells connected in series with the anodic current input leads of one cell connected with the cathodic current output leads of an adjacent cell. However, the principal inconvenience of such an anodic assembly is that it cannot be readily disassembled into its component parts. In effect, the anodes are permanently fixed to their support plate which forms an integral part of the anodic assembly. The anodic plates are thus not separable and the complete anodic assembly must be sent to the repair shop when the anodic coating becomes defective. However, the plate carrying the anodes is itself of titanium which increases considerably the investment in this metal for a given active surface. This major disadvantage is equally true of the titanium anodic assembly proposed in Netherlands Patent application 6704105 which moreover requires the presence of angles, bolts and nuts of titanium.

The present invention overcomes these disadvantages. The construction in accordance with the invention comprises a conductive and removable lateral wall of an electrolytic cell supporting the metallic electrodes of the same polarity and dividing the electric current between them. The wall comprises essentially an alternation of vertical portions of electrodes of the same polarity and elongated conductive elements disposed vertically between the edge portions of the electrodes and assembled one-by-one in a demountable manner by fastening means which assures individually the same selected pressure on each of the borders of the electrodes.

United States Patent C) 3,700,582 Patented Oct. 24, 1972 The invention is illustrated in the accompanying drawings which show by way of example a cell having a diaphragm supported by the cathodic lattice and anodes supported by a composite removable wall. The cell is suitable for the preparation of chlorine and caustic alkali by the electrolysis of a solution of alkaline metal chloride.

In the drawings:

FIG. 1 is a side view of an electrolytic cell having a removable wall in accordance with the present invention.

FIG. 2 shows respectively in end elevation and in crosssection along the line 22 of FIG. 1 two cells connected in series.

'FIG. 3 is a plan view of the two cells with one of the cells shown partially in horizontal section, and

FIG. 4 is a horizontal section on an enlarged scale of one end of an anode-carrying wall in accordance with the invention.

Each cell is composed essentially of a removable wall 1 supporting anodic leaves or plates, a cathodic casing 2 supporting the lattice and the diaphragm, a bottom pan 3 and a cover 4 provided with conduits for discharge of the chlorine and introduction of the brine. The anode plates 5 are formed of a film-forming metal coated with an operative electrode material, i.e., a metal or compound which is resistant to electrochemical dissolution in the cell and will function as an electrode. The bare material may, for example, be titanium, tantalum, zirconium, niobium, tungsten or an alloy of at least one of these metals. The coating is suitably one or more of the platinum group metals and their oxides.

The removable wall 1, shown in detail in FIG. 4, comprises essentially a series of elongated steel elements 6, 7 disposed vertically in side-by-side relation and separated by the vertical border portions of parallel anodes 5 which are clamped between successive wall elements. The thickness of the intercalated elements 7, which are all identical with one another, determines the distance between successive anode sheets 5. The end elements 6 (of which only one is shown in FIG. 4) provide for securing the wall 1 to end walls of the cathodic casing 2 in a fluid-tight, removable and electrically insulated manner by means of bolts 12. 'Inner faces of the elements 7 and end elements 6 are covered with a strongly adhering non-metallic coating resistant to the electrolyte of the cell. For example, the coating may be a protective layer of postchlorinated polyvinyl chloride 11 of which adherence to the elements of the wall 1 'is assured by an intermediate layer of polyester 10 firmly anchored by injection or compression in dovetail grooves or recesses 13 provided on the inner faces of the elements 6 and 7. The elements 7 are secured to one another by means of steel male-female threaded elements 9 of which an internally threaded portion at one end constitutes a nut and an externally threaded portion at the other end constitutes a bolt which screws into the nut of the adjacent threaded element. The end element 6 shown in FIG. 4 is secured to the adjacent element 7 by means of a steel nut 8, while the opposite end element (not shown in FIG. 4) is secured by a bolt screwed into the nut portion of the adjacent threaded element 9. A transverse slot 15 is provided in the round head 14 of each of the threaded elements 9 as well as the end nut 8 to receive a tool for turning the elements. The round head 14 of each of the threaded elements 9 and the nut 8 engages a shoulder 16 provided for this purpose within the thickness of each element so as to permit separately tightening each element to a predetermined pressure to assure an excellent electrical contact with the adjacent anodes 5. The body of each of the threaded elements 9 has a threaded end portion 17 of reduced cross-section constituting a bolt and a non-threaded intermediate section 18 having a cross-section between that of the head 14 and the threaded end portion 17. A tapped bore 19 extends into the head 14 and part of the intermediate portion 18 of each of the threaded elements 9 to constitute a nut. The threaded end portion 17 of each of the threaded elements 9 screws into the tapped bore 19 of the preceding threaded element or into the nut 8 of the end element. As seen in FIG. 2, holes 20 provided in the elements 6 and 7 and the vertical borders of the anodes for the passage of the threaded elements 9 are judiciously spaced in a vertical direction in a manner to permit applying a uniform pressure to the borders of the anodes.

On the side opposite the dovetail grooves 13, certain of the elements 7 which are uniformly distributed in the series of elements constituting, with the interposed perforated vertical borders of the anodes 5, the removable wall 1 are provided with copper input leads 21 for the anodic current so that the current is distributed uniformly throughout the assembly. To reduce the ohmic drop, the perforated borders of the anodes 5 as well as the contact surfaces of the elements 6, 7 are coated with metal having good electrical conductivity and preferably resistance to corrosion. For example, the contact surfaces are copper plated and then tinned or silvered. At the other side of the cell, the cathodic casing 2 is provided with outlet leads 22 for the cathodic current which are in line with the anodic leads 21 and at .the same height. The input leads 21 and output leads 22 of two adjacent cells in a group of cells connected in series are placed in alignment and very close to one another as seen in FIGS. 2 and 3. This permits an appreciable economy in the connections between the cells and a substantial reduction in the ohmic loss incident to the connections.

The cell assembly is supported by the input leads 21 and outlet leads 22 resting on conductive supports, insulated from ground, of T cross-section (FIG. 2) of which the vertical branch 23 is longer than the cell (FIG. 3) and has a downwardly facing central triangular cut-out so as to provide two opposite trapezoidal sections which meet at the center in an obtuse angle (FIG. 1). The horizontal portion 24 of the T-shaped support constitutes the support table proper of the two adjacent cells. The input leads 21 and outlet leads 22 are secured by means of bolts 25 (FIGS. 2 and 3) to conductive vertical metal plates 26 supported by the table 2. The plates 26 preferably have a certain flexibility in order to absorb individually the thermal expansion and contraction of each cell. By extending lengthwise beyond the cells, the vertical branches 23 of the T-shaped supports greatly facilitate the short circuiting of a cell by a very simple arrangement connecting successive supports.

The up-standing cover 4 in the form of a truncated pyramid is fixed to the cathodic casing 2 and the anode carrying wall 1 by means of bolts 27 while the bottom pan 3 is secured by bolts 28.

The cathodic casing 2 is fed with caustic alkali solution through a manifold 29 opening into the cell through tubes 30. Discharge of the solution from the cell is effected by tubes 31. Hydrogen is evacuated from the cathode compartment by a collector 32.

The anodes 5 are, for example, plane sheets of titanium not requiring any particular machining. The repair or the renewal of the coating constituting their active surface is efiected very easily. Once the cell has been shortcircuited by electrically connecting adjacent supports 23 and the cover 4 is removed, the bolts 12 and 28 which secure the anode carrying wall 1 to the cathodic casing 2 and the bottom pan 3 are removed and then the anode carrying wall 1 is removed upwardly. The anode carrying wall 1 is then disassembled by sequentially unscrewing the threaded elements 9 and removing the protective layers and 11. The anodic sheets 5 are then ready to be treated or replaced individually.

The renewal of the diaphragm supported by the cathodic lattice is effected in a similar manner by removing the cathodic casing 2 upwardly.

In comparison with bi-polar electrode cells occupying the same space, the cells of the present invention have the advantage of being able to take very high currents well above 20 KA and of requiring the disassembly of only a single cell for repairs, the other cells of the series continuing to function after short circuiting the cell that is to be repaired.

While the cell shown in the drawings and herein particularly described is designed for the preparation of chlorine and caustic alkali, it is evident that this description is only by way of non-limiting example and that the invention is applicable to cells for other purposes, for example the electrolytic preparation of chlorates.

What I claim and desire to secure by Letters Patent is:

1. An electrolytic cell having interleaved uni-polar vertical electrodes and a removable conductive outer wall supporting spaced parallel metallic plate electrodes of the same sign and distributing electric current to them, said wall comprising a series of independent like elongated vertically disposed metallic elements alternating with vertical borders of said plate electrodes, and threaded members for removably securing each said element individually to the next preceding element of the series, the border of each plate electrode being clamped between two successive said elements with equal pressure, said vertically disposed elements with the borders of said plate electrodes clamped between them constituting a continuous wall structure, each said threaded member having at one end a bored and tapped portion comprising a nut portion and at the other end a reduced externally threaded portion comprising a bolt portion adapted to be screwed into the nut portion of an adjacent like threaded member.

2. An electrolytic cell according to claim 1, in which at least a part of said elongated metallic elements regularly spaced in said series of elements are provided exteriorly with electric current input leads.

3. An electrolytic cell according to claim 1, in which each said threaded member has a head at said one end and a threadless intermediate portion of intermediate diameter between said head and said bolt portion, said tapped bore extending into said intermediate portion.

4. An electrolytic cell according to claim 1 having a base and a cover, in which said elongated metallic elements are provided with means for removably securing said wall to said base and cover respectively.

5. An electrolytic cell according to claim 1 having end walls perpendicular to said segmented wall, in which end elements of said segmented wall are provided with means for removably securing said segmented wall to said end walls.

6. An electrolytic cell according to claim 1, in which said electrodes supported by said segmented wall are plane metal sheets requiring no machining other than providing in a vertical border portion of the sheet holes for reception of said securing means.

7. An electrolytic cell according to claim 1, adapted to the electrolysis of a solution of alkaline metal chloride, in which said electrodes supported by said segmented wall are titanium plates at least partially coated with a material selected from the group consisting of platinum group metals and their oxides.

8. An electrolytic cell according to claim 1, in which border portions of said electrodes engaged by said elongated metallic elements and faces of said elements engaging said border portions of said electrodes are coated with copper and then with tin or silver to reduce the ohmic resistance between said elements and said electrodes.

9. An electrolytic cell according to claim 1, in which selected uniformly spaced elements of said series of metallic elements are provided with outwardly projecting input leads and in which outwardly projecting output leads are provided at the opposite side of the cell, further comprising electrically conductive supports insulated from ground and supporting said cell by said leads.

10. An electrolytic cell according to claim 1, in which said wall elements are provided on their inner face with recesses and with a protective non-metallic coating anchored in said recesses.

11. An electrolytic cell according to claim 10, in which said protective coating comprises two layers of which the inner layer next to said elements is anchored in said recesses.

12. An electrolytic cell according to claim 11, in which the inner layer of said coating comprises a mortar of polyester resin applied to the inner surface of said elements under pressure and the outer layer of said coating comprises postchlorinated polyvinyl chloride.

References Cited UNITED STATES PATENTS 3,563,878 2/1971 Grotheer 204-258 5 3,379,633 4/1968 Green 204-275 3,287,251 11/1966 Horne et a1. 204-270 FOREIGN PATENTS 1,160,999 8/ 1969 Great Britain 204-2'66 10 673,779 11/ 1963 Canada 204-275 JOHN H. MACK, Primary Examiner W. I. SOLOMON, Assistant Examiner 15 US. Cl. X.R. 

